Holmes isn't paying attention, but neither is the young weeping gentlewoman sitting in the eleventh row with the sore wrist (lots of writing recently) and faded, poorly fitted evening dress (borrowed) and the patched gloves (hard times) sitting with the still younger man in black with well-groomed whiskers, an ink stain on his bowtie (writer) and a crushed chrysanthemum in his front pocket (probably a poet, state of mourning, French) who has never worn a wedding ring (not her husband) on the hand with which he holds hers (romantic relationship) which has worn a wedding ring but is not currently (a widow or an estranged wife)...
I don't pretend to know anything about the Victorian era so I admit I made a lot of this stuff up. Despite having looked at a reference for opera glasses I don't think Holmes's are remotely accurate. I don't even know how that balcony works, or where their box is supposed to be in relation to anything...
I also don't know how hard/easy it was to get private boxes in opera houses if you weren't a nobleman or a character from The Picture of Dorian Grey. I suppose Holmes paid for it; it always seemed he was getting them private cars on trains, too.
FANTSTIC! I love the movement, I can see Holmes' eagerness and Watson's amusement, the angle, the simplicity of the colors, it's AWESOME